It was one of two waterspouts seen in the Channel Islands, with eyewitness accounts of another off Jersey.
Senior meteorological officer Martin Crozier said waterspouts were not uncommon, but were more likely to be seen during pleasant weather.
'They are like small tornadoes,' he said.
'Just a column of air that descends from the cloud.
'If they touch the water, which we believe this one may have done, they are called waterspouts.
'They are not that rare. I suppose they happen between three and six times a year on average.
